Compositional effects on the adhesion of acrylic pressure sensitive adhesives

The contact mechanics-based Johnson-Kendall-Roberts technique has been used to study the adhesion of cross-linked 2-ethylhexyl acrylate-co-acrylic acid (2EHA-co-AA) elastomers as models of pressure sensitive adhesives (m-PSA). We have addressed the effect of m-PSA composition on intrinsic solid surface energetics and on the mechanical performance of m-PSA. The measured surface energies of the m-PSA were all approximately 30 mJ m^-2, indicating surfaces dominated by methylene groups. The extent of adhesion hysteresis for the m-PSA used in our measurements was not a strong function of acrylic acid content implying that the main mechanism contributing to the adhesion of practical un-cross-linked or lightly cross-linked PSA is the viscoelastic dissipation. Several technical and physical issues concerning contact mechanical measurement of adhesion and the observed rate-dependent patterns of adhesion have been addressed.